In vitro effects of ultrasound with different energies on the conduction properties of neural tissue

The effect of ultrasound at various energy levels on the conduction properties of neural tissue is explored in this in vitro study. Excised sciatic nerves from the bullfrog were used for experiments. The nerves were stimulated by 3.5 MHz continuous wave ultrasound at 1, 2, and 3 W for 5 min. The peak-to-peak amplitude of the electrically evoked compound action potential (CAP) and the conduction velocity (CV) were measured in the nerves before and during ultrasound stimulation. The CV of the nerves increased by 5-20% for ultrasound stimulations at 1-3 W. The CAP amplitude increased by 8% during stimulation with 1 W ultrasound, and progressively decreased for 2 and 3 W ultrasound. This indicates that the effect of lower energy ultrasound increases both the CV and the CAP amplitude and that the reduction in the CAP amplitude for higher energy ultrasound is associated largely with ultrasonic thermal effects.     

Optically Activated Luminescence in a Natural Quartz

The spectral and kinetic characteristics of some natural quartz samples were studied by the method of optically stimulated afterglow. Defects with an unusually long time of luminescence decay of intracenter type ( = 179 msec, = 450 msec) have been revealed. Some of the parameters of these centers (stimulation and luminescence spectra, kinetics of afterglow decay, EPR spectrum, their temperature dependences, and also the stable behavior of these centers on exposure to thermal and optical effects) have been determined. Their role in the appearance of a luminescence signal ineffaceable in the process of formation of geological deposits and the possible processes leading to the afterglow of these centers are discussed.     

Study on cerebral microcirculation by Optical Doppler Tomography

Optical Doppler Tomography (ODT) provides a novel method to measure the blood flow velocity in vessels with the diameter at micrometer scale. Rats with cranial window are used as a model, and the changes in the blood flow velocity of cerebral arterioles in sensory cortex are measured in real time with an established ODT system, under electrical stimulation and drug administration. The results show significant differences in the blood flow velocity between experimental groups and control groups, demonstrating the feasibility of ODT in the cerebral microcirculation study. Compared with the conventional Doppler ultrasound, ODT provides much higher spatial resolution, and thus holds a promising future in the application of the cerebral microcirculation study, especially in the observation of the blood flow velocity in micrometer scale vessels. Supported by the National Hi-Tech Research and Development Program of China (863 Program)(Grant No. 2006AA02Z4E0), the National Natural Science Foundation of China (Grant Nos. 60378041, 60478040, 60878057 and 30770685), the Program for New Century Excellent Talents in University (Grant No. NCET-04-0528), and the Opening Project of MOE Key Laboratory of Laser Life Science, South China Normal University     

Canonical Tasks, Environments and Models for Social Simulation

The purpose of this paper is to propose and describe an alternative to an overarching theory for social simulation research. The approach is an analogy of the canonical matrix. Canonical matrices are matrices of a standard form and there are transformations that can be performed on other matrices to show that they can be made into canonical matrices. All matrices which, by means of allowable operations, can be transformed into a canonical matrix have the properties of the canonical matrix. This conception of canonicity is applied to three models in the computational organization theory literature. The models are mapped into their respective canonical forms. The canonical forms are shown to be transitively subsumptive (i.e., one of them is nested within a second which itself is nested within the third. The consequences of these subsumption relations are investigated by means of simulation experiments.     

Laser-induced vibrational excitation and desorption in the Cs/Cu(1 1 1) and Na/Cu(1 1 1) systems

The Cs/Cu(1 1 1) and Na/Cu(1 1 1) systems exhibit a transient excited electronic state localized on the adsorbate. Photo-excitation of this state triggers a motion of the alkali adsorbate away from the surface, leading to vibrational excitation of the adsorbate and possibly to desorption. A theoretical study of these photo-induced processes in the case of an exciting fs laser pulse is reported, based on a time-dependent approach of the adsorbate motion. The mean energy transfer from the laser photon energy to the adsorbate motion is shown to be weak, about 1% of the photon energy. Correspondingly, the vibrational excitation to high lying levels is very weak as well as the desorption process. The initial electronic state of the photo-induced process belongs to a continuum and vibrational excitation and desorption are found to vary rapidly with the energy of the initial electronic state. Initial vibrational excitation of the alkali adsorbate is also found to efficiently favour the desorption process, leading to a drastic variation of the desorption probability with the vibrational temperature of the adsorbate. The present results for the two systems are discussed and compared, in connection with available experimental data on these systems and on similar ones.     

Conductive stretchable shape memory elastomers combining with electrical stimulation for synergistic osteogenic differentiation

The natural extracellular matrix (ECM) possessed varying biomechanical properties which played important roles in the dynamic cellular microenvironment. However, for the conventional bone tissue engineering scaffolds, stretchability and shape memory property were normally absent. Thus, the behaviors of responsive changes required in dynamic physiological settings were unsatisfactory. Herein, a series of conductive polyurethane shape memory elastomers (PCL-IPDI-AT) were synthesized, which based on conductive amino capped aniline trimer (AT), isophorone diisocyanate (IPDI) and poly(ԑ-caprolactone) (PCL). The conductive elastomers possessed high elasticity and flexibility, especially, the breaking elongation of copolymer with 15% AT content was up to 570 ± 56%. The mechanical properties of elastomers could be adjusted by regulating the content of AT in copolymers. The conductive elastomers exhibited excellent shape fixity ratio and good shape recovery ability at 37 °C. The electrical conductivity of elastomers was measured via the standard van der Pauw four-probe method. They were all around 10⁻⁷ S/cm and similar to that in human physiological environments. On the one hand, excellent cytocompatibility was demonstrated by the viability and proliferation results of MC3T3-E1 pre-osteoblasts seeded on the elastomer. On the other hand, the elastomer could synergistically promote the osteogenic differentiation compared to PCL in terms of ALP activity, calcium deposition, and bone-related protein and gene expression levels as combined with electrical stimulation (ES). Specifically, the ALP activity for conductive elastomer under ES was notably improved by 1.4-fold compared to PCL at 7 days. Overall, the conductive elastomers displayed excellent stretchability, shape memory property, fatigue resistance and osteogenic bioactivity. They may be applied as bone substitutes for electrical-signal-sensitive bone tissue engineering.     

电刺激治疗神经系统损伤疾病：研究进展与展望

Nervous system injury can disrupt communications between neurons, leading to loss of basic nerve functions and even paralysis. The clinical prognosis of nervous system injury is usually poor. This adversely affects the physical and mental health of patients and their families, and causes serious economic losses to the society. Due to slow and incomplete healing, the regenerative capacity of the nervous system is limited. Despite development of various biomedical treatment options such as, stem cell transplantation, neurotrophic factors and scaffold application, it is still very difficult to achieve adequate therapeutic effects that can benefit clinical practice. It is worth noting that nervous system components are closely related to electric fields (EFs), and a fundamental property of neurons is plasticity in response to endogenous and exogenous electrical stimulations. Electrical stimulation has been applied by researchers to induce nerve repair. This review summarizes the progress in research on EFs on neurons and applications of EFs in the treatment of peripheral nerve system and central nerve system injuries, focusing on the methods and effects of electrical stimulation. Research using direct, alternating, and pulsed EFs, with various parameters, has all demonstrated its positive effects on nerve healing and motor function recovery. Research on nanogenerators (NGs), a novel electrical stimulation technology that can convert mechanical energy into electrical energy, has achieved great progress in recent years. In biomedicine, NGs can collect the mechanical energy of human motion and convert it into electrical stimulations without requiring an external power supply, which can lead to significant innovations in electrical stimulation therapy. This review also discusses the recent applications of NGs in the treatment of nervous system diseases. NGs can be used to fabricate miniature, ultra-thin, flexible, and biodegradable healthcare devices according to different application scenarios such as in vivo or in vitro. NGs have enabled specific applications in deep brain stimulation, peripheral nerve stimulation, muscle stimulation, and sensory substitution to restore nervous system function. In order to apply electrical stimulation therapy in the clinical setting and improve the quality of life of patients with neurological injuries, further research into stimulation devices and their settings and parameters is highly desirable.     

大口径高通量三倍频研究

为考核神光Ⅱ升级项目三倍频输出能力,以及研究高功率激光驱动器高通量三次谐波转换过程中相关技术问题,在神光Ⅱ第九路上开展了一轮'Ⅰ+Ⅱ’三倍频实验,实验中三倍频最大输出达到2740 J,最大输出能通量达到3.6 J/cm²以上,最大转换效率为~63%;根据实验结果结合理论分析,初步研究了影响效率转换主要参量;在实验中观察到时间相位调制所引起的振幅调制,以及横向受激拉曼散射所引起的破坏. 实验结果有效验证了神光Ⅱ升级的倍频器的相关设计程序和参数,以及神光Ⅱ升级项目的三倍频输出能力. 关键词： 非线性光学 三次谐波转换 高通量 时间相位调制     

通过金属离子刺激调节金属有机骨架结构用于光催化CO2还原

通过自组装得到一种具有适中配位键强度和适度骨架柔性的二维Cd基金属有机骨架(MOF){[Cd (HL)(BPY)_0.5(H₂O)]·2H₂O}_n(1),其中H₃L=4,4′,4″-(亚硝基三(亚甲基))三苯甲酸,BPY=4,4′-联吡啶)。由于其独特的结构特征,在金属离子(Zn²⁺/Ni²⁺/Co²⁺)刺激下,1逐渐转变成相应金属离子主导的MOF结构2、3和4。在此过程中,随着金属离子Cd²⁺→Zn²⁺、Cd²⁺→Ni²⁺和Cd²⁺→Co²⁺的交换,1通道中自由的Cd²⁺和L3-与MOF的骨架进行融合,导致通道空间的扩大,发生次级构筑单元(SBU)的转变,进而形成可调节的骨架。光催化二氧化碳还原结果表明,由离子交换所得到的新结构在催化效率上并没有很大改观,但在产物选择性上却有极大地提升(其中配合物3展示出100%的CO选择性)。